Voltage regulator tube



March 19, 1940. J, PQMFRETT 2,194,432

VOLTAGE REGULATOR TUBE Filed Jan. 25, 1959 IN V EN TOR.

A TTORNEYS.

Patented Mar. 19, 1940 UNITED STATES PATENT OFFICE vonmcs REGULATOR TUBE Appllcation'lanuary 25, 1939, Serial No. 252,739

1 Claim.

This invention relates to voltage regulator tubes and more especially to tubes of the type employing a gaseous discharge for voltage regulation.

A principal object is to provide a voltage regulator tube of the cathode glow type which possesses high operating stability even at relatively low current drains in the system to which it is connected.

10 Another object is to provide gaseous voltage regulator tubes of the cathodic glow type with a construction such that the electrical characteristics of large batches of tubes are uniform, thus enabling the tubes to be manufactured in large 1 quantities with uniformity of results when the tubes areused in circuitswhose voltage is to be controlled.

Another object is to provide an improved gaseous voltage regulator tube wherein the electrodes are so constructed and arranged as to insure a definite breakdown voltage.

A feature relates to a voltage regulator tube of the gaseous discharge type wherein the elec-.

trodes are constructed and arranged so that the "breakdown" voltage is always in excess of the operating voltage.

A further feature relates to the novel organization, arrangement and relative location of parts which constitute a more efiicient and stable voltage regulator tube of the cathodic glow discharge type.

Other features and advantages not specifically enumerated will be apparent after a consideration of the following detailed descriptions and u the appended claim.

Referring to the drawing, there is illustrated one preferred embodiment wherein Fig. 1 is an elevational view, partly sectional, of a tube according to the invention.

a Fig. 2 shows a series of curves explanatory of the operation of the tube of Fig. 1.

While electric gaseous tubes of the cathodic'glcw discharge type have been proposed heretofore as voltage regulatorsv in many kinds of electrical 4| circuits, considerable difficulty has arisen because the breakdown" or striking potential has been very close to the operating or keep alive" potential. This is especially true where the tube has an operating potential which is in excess 50 of 100 volts. In this latter case where the breakdown potential is equal to or less than the operating" potential, considerable instability occurs when the device is used with circuits of low current drain. For example. where J the tube is used to regulate the anode or grid (on. asp-27.5)

potential of an audio amplifier tube, such as is used for example in radio receivers and the like, this instability is the cause of much noise in the output of the amplifier. I have found that this disadvantage, amongst others, can be overcome by proper design and location of the starting electrode with respect to the cathode and anode of the regulator tube, and as a result of which the breakdown" potential ,is always in excess of the operating potential. 1

Referring to Fig. 1, there is shown a typical embodiment wherein the tube, which may be of any configuration, comprises an enclosing envelope I of glass or metal. In the case of the glass envelope, it is provided with the convenu tional .reentrant stem 2 terminating in a press 3, wherein are sealed the various lead-in wires 4,

5 and 6. The wire 5 is connected to a metal rod which, at its lower end, is sealed into the press 3. Rod 8 constitutes the anode of the tube m and may be of nickel, or other suitable metal. Likewise, a pair of lateral metal support rods 9 and H) are sealed into the press, rod 9 being connected to lead-in wire 4. Welded or otherwise fastened to the side rods, 9, I0, is a tubular or cylindrical metal electrode H which functions as the cathode. Electrode ll may be of any suitable metal such for example as nickel, and may have its inner surface activated or unactivated. For example, the cathode surface a may be activated by coating it with electronemissive material wellknown in the radio tube art. Preferably, the anode 8 is circular in crosssection and is mounted so as to be concentric with cathode ll.

Attached to the inner face of cathode ll adjacent the upper end, is a starting electrode l2 which may be of nickel, or other suitable metal, which is preferably bent to L-shape with the horizontal part of the L extending radially ino ward toward the anode 8 so that the said horizontal part is in line or approximately so with the upper end of the cathode. The vertical part of electrode i2 may be welded to cathode H. In accordance with the invention, the horizontal 5 arm of electrode 12 extends inwardly so as to be closely adjacent to, but slightly spaced from, anode 8, for example this spacing may be about 1 mm.

In order to preserve the concentric relation 50 and spacing of the electrodes, a pair of insulator discs l3, l4, may be assembled over the rods 9, l0 and anode 8. These discs may be of mica and fastened in place in any manner wellknown in the radio tube art, for example by being provided with metal eyelets which are welded to the rods 9 and Ill. The discs I3 and it closely fit against the upper and lower ends of the cathode so as to confine the discharge to the in ner surface of the cathode. Preferably, the portion of anode 8 which extends beneath mica disc I3 is provided with an insulator protective sheath in the form of a glass or ceramic tube I5, thus confining the discharge to the space enclosed by the cathode II and discs I3 I4. A getter support I6 carrying a suitable getting material may be connected to wire I1 which is sealed into the press and connected to lead-in wire 6. If desired, the disc I4 may contact resiliently with the dome of bulb I in any manner wellknown in the radio tube art to steady the electrode assembly against shock or vibration. The envelope I is filled with a suitable gaseous atmosphere such as a mixture of one or more of the rare gases, and pressure and nature of this gas mixture and the nature of the cathode surface determining the voltage regulation characteristics as is wellknown in the art of gaseous discharge tubes.

In manufacturing the tube, the glass envelope I is carefully exhausted while being heated at a temperature of approximately 450 C. for approximately 15 minutes. The envelope is allowed to cool, after which the cathode is heated to redness by any well-known means, for example by high frequency induction, until all occluded gases are removed therefrom. The getter material on support I6 is then flashed to perfect the vacuum, and the device may then be filled with the proper gas or gas mixture at a predetermined pressure after which the envelope is sealed off in the well-known manner. The bulb may be provided with any well-known form of shell base I8 canying the contact prongs I9 to which the various lead-in wires are connected. While Fig. 1 shows a base of the Octal type, it will be understood thatthis is merely illustrative.

Fig. 2 illustrates the voltage E against current I characteristics of the two types of voltage regulator devices the curve designated A represents the voltage current characteristics of a tube such as shown in Fig. 1 wherein the starting electrode is located near one end of the cathode 8, while the remaining curves BI, B2 and B3 show the characteristics for tubes where the starting electrode is located near the center of the cathode structure. It will be observed that with a tube such as shown in Fig. 1 and illus-' trated by curve A, the breakdown" voltage is in excess of the operating voltage, whereas in the curves Bl, B2 and B3 the breakdown voltage is less than the operating voltage. The tubes with the characteristic B therefore, show unstable operation and noisy performance whereas the tube of Fig. 1 exhibits stability of operation and freedom from noise. It has been found that with the construction of Fig. 1, the discharge is always initiated between the starting electrode and the anode, this breakdown voltage being slightly higher than the rated operating voltage, After the discharge is initiated, the cathodic glow travels along the surface of the cathode, the amount of the discharge depending upon the current being drawn. Probably one explanation for this is that placing the starting electrode as shown in Fig. 1, it is located at a point where the field strength between the anode and cathode is relatively weaker than exists between the anode and the central portion An electric regulator tube of the gaseous dis- 

